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Physical activity curbs insulin production

Insulin is an essential hormone for humans and many other animals, helping to regulate sugar metabolism. In order to clarify how this process functions, a team of researchers led by the Julius Maximilians University of Würzburg (JMU) has used the fruit fly Drosophila melanogaster as a case study.

While this fly also secretes insulin after meals, this hormone does not come from the pancreas as in humans, but is instead released by nerve cells in the brain. By measuring the activity of insulin-producing cells in walking and flying Drosophila, the experts found that physical activity has a strong effect on these cells: when the fly starts to move, its insulin-producing cells are immediately inhibited, whereas when it stops moving, the activity of these cells rapidly increases and rises above normal levels. According to the scientists, the fast, behavior-dependent inhibition of insulin-producing cells is actively controlled by neural pathways.

“We hypothesize that the low activity of insulin-producing cells during walking and flight contributes to the provision of sugars to meet the increased energy demand,” said study lead author Sander Liessem, an expert in Neurobiology and Genetics at JMU. “We suspect that the increased activity after exercise helps to replenish the fly’s energy stores, for example in the muscles.”

The researchers argued that, although the release of insulin in fruit flies is mediated by different cells than in humans, the insulin molecule and its functions have not changed much in the course of evolution. Thus, these findings could contribute to human health too, by highlighting a possible link explaining how physical activity could positively affect insulin regulation via neuronal signaling pathways.

In future studies, the scientists aim to investigate which neurotransmitters and neural circuits are responsible for the activity changes observed in insulin-producing cells in flies, and what other factors – such as the age of the flies or their nutritional states – could have an influence on these cells. Ultimately, the researchers plan to bring these two questions together: how does the brain control movement, and how does the nervous system ensure that the energy balance is regulated accordingly?

The study is published in the journal Current Biology.

By Andrei Ionescu, Staff Writer

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